Tachometer systems are generally used to measure speed of rotating wheels. During installation, a tachometer system is usually mounted at a position exterior to an axle of a wheel since the axle is a compact monolithic component that has little or no space to accommodate the tachometer system internally. Further, the tachometer system, when mounted in an environment open to atmosphere, is subject to dirt, grime, soil, water and chemicals which may interfere with the working of the tachometer system. Furthermore, the tachometer system may be also subject to physical damages due to collision with undesirable matter such as sand, stones, rocks and dirt. Furthermore, the damage may be enhanced when subjecting the tachometer system to a high pressure wash of the vehicle. Hence, an externally mounted tachometer system lacks protection and durability. Subsequently the externally mounted tachometer system entails frequent cleaning, maintenance and replacement in such a mounting arrangement.
German Patent 19625746 ('746 patent) relates to a tachometer system including at least one sensor surrounded by a sensor housing arranged on a wheel carrier of a non-driven wheel. The tachometer system further includes a rotor magnetized in sections and fastened to a hub region of the wheel. The sensor and the rotor are housed in a central hub cavity. The rotor is therefore located in one section of the hub cavity, whereas the sensor is fastened via the sensor housing thereof to the free end of an axle pin projecting from the wheel carrier. Access can easily be gained, in the hub cavity, from the outside of the wheel to the tachometer system. However, the '746 German patent discussed above lacks a capability of accommodating a fluid substance in the axle pin and a pressure equalization system in place to maintain a safe working pressure of the fluid within.